handler.h

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// handler.h --
// $Id: handler.h,v 1.11 2003/11/23 01:42:51 wcvs Exp $
// This is part of Metakit, the homepage is https://www.equi4.com/metakit/

#ifndef __HANDLER_H__
#define __HANDLER_H__

// Declarations in this file

  class c4_Handler;         // data representation handler

//  class c4_Sequence;
    class c4_HandlerSeq;      // a sequence built from handlers

  class c4_Column;          // not defined here
  class c4_Field;           // not defined here
  class c4_Persist;         // not defined here
  class c4_SaveContext;       // not defined here


class c4_Handler
{
  c4_Property _property;

public:
  c4_Handler (const c4_Property& _prop);
    //: Constructor (this is an abstract base class).
  virtual ~c4_Handler ();

  virtual void Define(int, const t4_byte**);
    //: Called when the corresponding table has been fully defined.
  virtual void FlipBytes();
    //: Called to reverse the internal byte order of foreign data.
  virtual void Commit(c4_SaveContext& ar_);
    //: Commit the associated column(s) to file.
  virtual void OldDefine(char, c4_Persist&);

  const c4_Property& Property() const;
    //: Returns the property associated with this handler.
  int PropId() const;
    //: Returns the id of the property associated with this handler.

  void ClearBytes(c4_Bytes& buf_) const;
    //: Returns the default value for items of this type.

  virtual int ItemSize(int index_) = 0;
    //: Return width of specified data item.
  void GetBytes(int index_, c4_Bytes& buf_, bool copySmall_ =false);
    //: Used for backward compatibility, should probably be replaced.
  virtual const void* Get(int index_, int& length_) = 0;
    //: Retrieves the data item at the specified index.
  virtual void Set(int index_, const c4_Bytes& buf_) = 0;
    //: Stores a new data item at the specified index.

  int Compare(int index_, const c4_Bytes& buf_);
    //: Compares an entry with a specified data item.

  virtual void Insert(int index_, const c4_Bytes& buf_, int count_) = 0;
    //: Inserts 1 or more data items at the specified index.
  virtual void Remove(int index_, int count_) = 0;
    //: Removes 1 or more data items at the specified index.
  void Move(int from_, int to_);
    //: Move a data item to another position.

  virtual c4_Column* GetNthMemoCol(int index_, bool alloc_ =false);
    //: Special access to underlying data of memo entries

  virtual bool IsPersistent() const;
    //: True if this handler might do I/O to satisfy fetches

  virtual void Unmapped();
    //: Make sure this handler stops using file mappings

  virtual bool HasSubview(int index_);
    //: True if this subview has materialized into an object
};


class c4_HandlerSeq : public c4_Sequence
{
  c4_PtrArray _handlers;
  c4_Persist* _persist;
  c4_Field* _field; 
  c4_HandlerSeq* _parent;
  int _numRows;

public:
  c4_HandlerSeq (c4_Persist*);
  c4_HandlerSeq (c4_HandlerSeq& owner_, c4_Handler* handler_);

  virtual int NumRows() const;
  virtual void SetNumRows(int);
  
  virtual int NumHandlers() const;
  virtual c4_Handler& NthHandler(int) const;
  virtual const c4_Sequence* HandlerContext(int) const;
  virtual int AddHandler(c4_Handler*);

  void DefineRoot();
  void Restructure(c4_Field&, bool remove_);
  void DetachFromParent();
  void DetachFromStorage(bool full_);
  void DetermineSpaceUsage();
    
  c4_Field& Definition() const;
  const char* Description();
  c4_HandlerSeq& Parent() const;
  virtual c4_Persist* Persist() const;
  
  c4_Field& Field(int) const;
  int NumFields() const;
  char ColumnType(int index_) const;
  bool IsNested(int) const;
  
  void Prepare(const t4_byte** ptr_, bool selfDesc_);
  void OldPrepare();

  void FlipAllBytes();
  void ExchangeEntries(int srcPos_, c4_HandlerSeq& dst_, int dstPos_);

  c4_HandlerSeq& SubEntry(int, int) const;
  
  c4_Field* FindField(const c4_Handler* handler_);

  void UnmappedAll();
  
  static void BuildMeta(int, int, c4_View&, const c4_Field&);

protected:
  virtual c4_Handler* CreateHandler(const c4_Property&);

  virtual ~c4_HandlerSeq ();
};


#if q4_INLINE
#include "handler.inl"
#endif


#endif

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Metakit C++ API Reference - https://www.equi4.com/metakit.html - extracted with Doxygen